Some chair support structures have been constructed solely of pure tension members and pure compression members. For example, rocking chairs have been provided by support structures having two rigid (i.e., compression) members that each have upper end portions that are spaced from each other and lower end portions that are spaced from each other. The rigid members are oppositely inclined with respect to the horizontal, intersecting each other in side view, and one of the rigid members is positioned intermediate the other. The rigid members are connected to each other near their bottoms by one pair of flexible tension members that prevent the bottoms from sliding apart, and they are also connected above where they intersect by another pair of flexible tension members that prevent the rigid members from falling owing to gravity. The rigid members can pivot about their points of contact with the ground, providing the rocking movement.
Meeker U.S. Pat. No. 1,969,313, Robeson U.S. Pat. No. 4,118,064 and Gilbert U.S. Pat. No. 4,251,106 disclose examples of such support structures for rocking type chairs having seating surfaces provided by sling-type flexible sheets suspended between the upper ends of the rigid members. Meeker and Robeson disclose structures in which each rigid member is a pair of parallel struts connected to each other by horizontal bars and teach that the structures can be modified to prevent rocking by adding pin connections between the rigid members where they intersect. Gilbert discloses a structure in which the rigid member that is longer than the other has a central portion that branches at the lower end to provide two feet and at the upper end to support a sling-type seating surface flexible sheet that also acts as an upper tension member preventing the rigid members from falling owing to gravity; backward pivoting is prevented beyond a certain point by interference of the branched lower ends of the longer rigid member with the diverging lower ends of the other rigid member, and forward pivoting is prevented beyond a certain point by a pair of cords between the rigid members at positions to the rear of where they intersect each other in side view.